AbstractDifficulty in the removal of calcium carbonate by filtration in the preparation of cyanamide by passage of CO2 through an aqueous slurry of the calcium salt, is overcome by dissolution of the salt in an aqueous solution of cyanamide before passage of the CO2. A large laboratory apparatus is described for this process, by which high yields are obtained. Stable solutions of cyanamide of 60% concentration or 95% pure solid material can be prepared which are very convenient for the preparation of cyanamide derivatives, several of which are described.